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[Articles Home]  [Add Article]  

A Little Mobile Information

Alan Applegate (K0BG) on January 5, 2003
View comments about this article!

I am 62 years of age, I have been mobiling for some 30+ years, and I've owned or driven over 20 vehicles. And if I've figured correctly, I've driven nearly 4 million miles in my life. I've worked for a two-way radio shop installing radios, for a wholesale distributor selling radio equipment including amateur gear, and I've owned 14 different transceivers, all of which have been operated mobile except for one. I've built two HF mobile amplifiers, owned two different commercial amplifiers, and built more mobile antennas than you can imagine. I'm sure there are a few folks who have driven more miles, some who have owned more rigs, used more (different) antennas, and quite a few who have been licensed longer. And maybe some of you out there have worked more than 299 countries mobile. But none have enjoyed the hobby more.

Over the years, I have discovered a few tricks, which make mobile operation more enjoyable, less tiresome, and most importantly safer. I wish to share some of these with the readers of eham.net. You may comment as you please, or differ from my views; I only offer them as a guideline.

First, I believe in doing the job correctly. To me, there is no "temporary" mobile installation as this denotes an installation with poor results and a lack of safety concerns. This goes for both rig and antenna mounting. More on this later…

Safety is the most important issue, period! The rig (or the control head) needs to be close at hand, the display needs to be readable, and the controls accessible. And it should be positioned in such a way to avoid interference with passive restraints (airbags), and operating controls including dangling microphone cords.

Mounting techniques seem to suffer when it comes to mobile operation. Velcro, bungee cords, nylon or canvas straps, and duct tape are not adequate. Imagine an 8-pound rig traveling through the air at 60 mph (88 fps). That's 30 tons of potential energy (mass times the velocity squared)! The best strategy is simple. Think about the worse thing that could happen. If you don't, it will! The last three cars I have owned have had mounting screws below the AM/FM radio, which I used to mount the rig (control head). Your case it may not be as simple, and the Mobile Forum is a good place to start looking for ideas.

Wiring is the next most important item. Cigarette lighter sockets (auxiliary power outlets) are out! No matter the total current draw of your HF rig, the minimum wire size should be AWG # 6, and connected directly to the battery! This has more to do with noise introduction, than it does power draw. Properly fuse both the negative and positive leads as close to the battery as possible, and dress the leads to avoid sharp edges, and securely attach them with tie wraps. A variety of connectors are available for interconnecting just about any conceivable combination. Fastenal or your local mobile sound shop are good places to start looking for connection devices. Radio Shack is also a good source. Buy a complete set of fuses for the vehicle, rig, etc. and put them in the glove compartment. If you don't, you'll wish you had.

Don't use a cheap antenna! Any good, well-built multi-band antenna is going to cost upwards of $250. This is one area you do not want to scrimp on.

With the exception of 10 and maybe 17 meters, it is difficult to mount a full-length 1/4 wave antenna which means the antenna must have a loading coil to cancel the capacitive reactance due to the shortening. Physically small coils with metal endcaps, or helically wound fiberglass antennas maybe esthetically pleasing, but their performance suffers when compared to the "Texas Bug Catcher" types.

Spirally wound short antennas on 75 and 40 meters exhibit no more than one or two percent efficiency. Add a poor mounting location and attachment method, and you'll be lucky to get that much, hence the moniker dummy load on a stick! This is because their coils are very low Q, typically less than 50 and as low as 10! Q is the ratio of reactance to resistance, and the higher the Q the better. Most commercial screwdriver antennas exhibit a Q of between 100 and 350 depending upon band (regardless of what you read). Under very special conditions coil Qs as high as 800 or more are possible, but they are large and not ideal for mobile operation.

A typical 9 foot, center loaded, mobile antenna will have a radiation resistance of 12 ohms or so. A requisite loading coil with a Q of 50 will have a loss of 15 ohms. At a Q of 300 the loss will be just over 2 ohms. Add in a poor mounting technique with its inherent losses, and it is easy to see why minimizing losses is important.

And don't mount with duct tape, license plate mounts, trunk lip mounts, magnet mounts, or worse, bumper mounts. There is no excuse you can give me for not drilling holes for a good ball-mount or base plate. Either you're into mobile operation or you're not. But if you just can't bring yourself to drilling holes, then check Don Johnson's book "Moblileering" or the ARRL Antenna Compendium Volume 7 for alternate frame mounting techniques. But remember…

The closer to the ground you mount an antenna, the greater the ground losses. For example, an average 9 foot 75 meter antenna mounted on the bumper (or trailer hitch mount) will exhibit a ground loss of about 10 ohms. The same antenna mounted on the trunk will be about 8 ohms. Mounted on the roof it will be about 4 ohms. With the radiation resistance about one ohm on this band, it doesn't take a rocket scientist to figure out why mounting position is important. No matter where or how you mount it, the coil should be at least 18" above the nearest metal, albeit difficult on some vehicles, especially vans where front mounting may be your only alternative.

A recent post on the Mobile Forum asked the question, "Just how high can a mobile antenna be"? I personally have used a full 1/4 wave 20 meter antenna. There was a center spring, which allowed the top 8 feet to lay back and clear 13.6 bridges if I was going fast enough. At a standstill, the top was 21 feet off the ground. Here in the Desert southwest where I live, 16 feet is about the limit albeit my current antenna is 16'8" at the tip. There are only a few spots in town where it hits and I know every one of them! Recent trips to Denver, and Lubbock, proved this length will work at least in this part of the country. By the way, only California has a height law, which covers mobile antennas. Sixteen feet in case you're wondering. And another in case you're wondering; a 16 foot 20 meter antenna under proper conditions will be 6 db louder than an 8 foot one.

A recent addition to the amateur arsenal is the automatic antenna tuner. A lot of hams shy away from them because they have been told they're inefficient. They're not and they're not inexpensive, but their convenience may offset the latter. While it is true that a base-loaded whip (as used with most auto-tuners) is less efficient than a good center loaded, resonant antenna, in some cases the overall losses are less. I use one with a 20-meter resonant antenna to tune it for the other bands I occasionally work. Fact is on 40 meters, I get better signal reports with the combination than I do with the 40 meter resonate coil installed. The best part is I can QSY in just a few seconds. If you band hop a lot, this may be your best bet. Just don't try to use one with a helically wound antenna to band hop. The distributed capacitance is just to high to allow this type of operation.

Noise abatement is the most overlooked aspect in mobile operation. For about $50 and a couple of hours your vehicle can be as quiet as your base station. Call Palomar Engineers, RF Parts, or Amidon and buy a handful of clip-on split ferrite beads. Not just any snap-on bead will work. Mix 43 is best for HF operation as its cutoff frequency is about 1 MHz. At 15 MHz, the loss increases to about 100 ohms, which is significant if the circuit they're attached to is near zero ohms. Now you know why it is important to use a large sized wire for power feeds.

Here's where they go: Around the battery-connected power leads (+ and-) just where they enter the interior of the vehicle. Believe it or not, around the spark plug wires as close to the coil-pack or distributor as possible (assuming you have wires, some new vehicles don't and here they go around the coil control wires), fuel injector harness(s), electric fuel pump leads, heater fan leads, and perhaps the windshield wiper leads. Using the noise blanker in most rigs causes more problems than it cures. If you have to use one, you haven't done a good job at noise abatement. My personal car is dead quite except on very hard acceleration where it is just audible. Yours can be too, but buying a diesel isn't a cure-all either as some models are noisier than gas engines.

When you're doing all of this installation, wiring, etc., don't forget to use good safe practices when soldering, crimping, connecting to the battery, running control cable, power cables, and coax. An ounce of prevention is worth a pound of cure as the old adage says.

And keep reading the Mobile Forum for more good ideas.

Alan Applegate, KØBG

Member Comments:
This article has expired. No more comments may be added.
 
A Little Mobile Information  
by KA0MR on January 5, 2003 Mail this to a friend!
Alan-
By far the most comprehensive how-to-do-it-right one can come up with. I too have went mibile and discovered what you have.

Take Alans advice it is sound advice.
 
A Little Mobile Information  
by KD5FOY on January 5, 2003 Mail this to a friend!
simply stated, an outstanding article on how to do it
right. very well done indeed!!!

larry
kd5foy
 
Tip for reducing ground losses with a removable mo  
by N4ZZK on January 5, 2003 Mail this to a friend!
Good article Alan. Here is a tip to add to your comment about getting the base of the antenna off the ground as much as possible. If you want the convenience of a removable mount using a trailer hitch receiver, use an inverted "drop hitch" to get the base up another 8" or so.

You can see the one I assembled at:

http://www.mindspring.com/~aludwick/al.htm

73, Al

P.S.
Although I haven't got nearly the experience mobiling as you, I've come to a lot of the same conclusions about the antenna setups, grounds, etc. I'm using a K2 with 10 watts so its probably more important to aim for an efficient antenna setup. I had good luck and worked DX with the K2.
 
RE: A Little Mobile Information  
by AA4PB on January 5, 2003 Mail this to a friend!
Good Job! Just a question/comment about the use of ball mounts. I always used to use them - they are certainly the strongest mount. The problem I've run into with recent vehicles however is that the sheet metal is so thin that the whole body flexes and the mount moves. I worry about eventual metal fatigue and that has caused me to look for other alternatives.
 
RE: A Little Mobile Information  
by N4HRA on January 5, 2003 Mail this to a friend!
A Simple trick I have used for when I was in CB years ago and
now with ham radio is ground the tail pipe to the frame at the
back of the vehicles. this is all I have ever used.
With 1 vehicles it cut the engine noise from +20 to almost 0.
With my Caravan it even cut the engine noise on the broadcast radio.
My Reason it works: look at the engine as a spark gap xitter, the
tail pipe is grounded to the engine and acts like a antenna.
 
RE: A Little Mobile Information  
by N4HRA on January 5, 2003 Mail this to a friend!
A Simple trick I have used for when I was in CB years ago and
now with ham radio is ground the tail pipe to the frame at the
back of the vehicles. this is all I have ever used.
With 1 vehicles it cut the engine noise from +20 to almost 0.
With my Caravan it even cut the engine noise on the broadcast radio.
My Reason it works: look at the engine as a spark gap xitter, the
tail pipe is grounded to the engine and acts like a antenna.

73s
Lew
N4HRA
 
RE: Mobile operation  
by W0JOG on January 5, 2003 Mail this to a friend!
I've been mobiling about as long as advertised above and agree with most of what is said.

I disagree, however, with the statement "Any good, well-built multi-band antenna is going to cost upwards of $250." Not unless Hustler has raised its prices a great deal. I've used the Hustler system for 40 years without a problem or a noted loss of signal over any other mobile antenna type.

And, when mounting on a van (we have a GMC Vandura 2500 conversion van), I came up with a sturdy and effective mount by having a local metal fabricator make me a 2 inch by 20-or so inch strap, drilling it for U bolts where needed and at the top end for a Radio Shack part no. 940-0913, a "3-way Mirror Mount.:

The "L" part is affixed to the top of the strap. The strap is bolted to the spare tire mount. The Hustler breaks over parallel with the roof when retracted and stands well above the 18-inch recommended height for the coils when in use.

Antenna tuning is augmented with MFJ-910, a little match box of capacitors. It is at the base of the antenna, just inside the rear van door where the lead comes in. The coax lead in through the door is the only hole drilled in the van for this system.

It has worked for years, all bands, 80-10 meters.
 
A Little Mobile Information  
by W4WB on January 5, 2003 Mail this to a friend!
Excellent article. I suggest that the selection of Type 43 material for the ferrite is not as desirable as using Type 73 or 77 material for use in the HF spectrum. Type 43 is better for the 6 m to 70 cm bands. You will find 73/77 quite superior for 30-80 m in particular. I note that Type 43 is widely available, but the listed sources generally have 73 or 77 beads in stock as well.

 
A few notes and corrections...  
by KC0LPV on January 5, 2003 Mail this to a friend!
Good article--I definitely need help figuring out how to do a decent mobile dual-band installation on my '98 Neon Coupe.

A few issues:

1.) mass x velocity(squared) is KINETIC energy, not POTENTIAL.

2.) You should not fuse the ground side supply. If the ground side opens prior to the positive side, the unit will ground through the mount OR the coax braid--not good. Never fuse the ground side.

3.) No trunk lip mounts? Do you realize that some people lease there vehicles? Or that some people do not wish to cut permanant holes into their vehicles, myself included? Yes, we trade off some choice in where to mount the antenna, but a good trunk lip mount can be all but "permanant".

4.) I'm not 100% sure on this one, but I'm pretty sure that in my state, it would be illegal to run an antenna which is 21 feet tall, even if you did have it "bend over" when you're at speed.

Jim
 
A Little Mobile Information  
by K6NT on January 5, 2003 Mail this to a friend!
Very good article. Regarding ferrite types. My club and I have done extensive testing of ferrites as chokes, using an antenna analyzer. We have found that the 43 mix is better than 77 mix at frequencies above 7 MHz and the 77 mix is better than the 43 mix below 7 MHZ. Since 43 mix comes in split beads and not 77 mix, this is what you should use......however,

There is a new mix, 31, that comes in split beads. It appears to be better than 43 mix below 18 MHz, and 43 is better than 31 above 18MHz. However, they both work real well throughout the HF frequencies and 50 MHz, so use either one.
 
RE: A Little Mobile Information  
by K0BG on January 5, 2003 Mail this to a friend!
A few comments on the mix of ferrite beads, and commercial antennas

Mix 43 has a cutoff of 1 Mhz. Mix 77 has a cutoff of 2 Mhz. I suppose there isn't much difference in the real world if you have a low impedance feed. But...Mix 77 only offers about 50 ohms at 10 Mhz, while mix 43 is about 80 ohms at 10 Mhz. This notwithstanding, either works well enough in most cases. A call or e-mail to Palomar Engineers and Jack Althouse will send - free of charge - a brochure listing the various types and their suitibility for choking RFI, and it is worth the read.

One respondent mentioned Hustler antennas, which incidentally is the most popular HF mobile antenna out there. Dr. Jerry Sevick wrote a series of articles for QST dealing with short verticles. Part of the research behind those articles were never published in QST. However, they are added as appendixes to his book "Building and Using Baluns and Ununs"published by ARRL. In these appendixes are graphs showing the Q and efficiency of Hustler and homebrew coils on 40 and 80. It too is worth the read.

I don't try to bash any brand of antenna, save for a few of the cheaply made helical wound ones. As Don Johnson, W6AAQ, aptly put it, they are dummy loads on a stick! But 6 db is 6 db and if you want to be heard in the pileups, every little bit of signal you can muster makes you stick out above the rest.

I am, however, an advocate of auto-tuners, and one of these days I plan to write a comprehensive article about their efficiency (or lack of it). Fact is, they are not as bad as you might expect.

I thank everyone for their comments, good and bad. This has been fun, no matter the outcome.

73 and good mobileing.

Alan, KØBG
 
A Little Mobile Information  
by WD4HVA on January 5, 2003 Mail this to a friend!
There is nothing that will match the sight of your two-hundred and fifty dollar antenna bouncing and disintegrating at the end of the coax cable in your rear view mirror!

I had a Texas Bugcatcher - the big coil version, with the five foot mast and a six foot whip. It was mounted using a frame mount off the back of my 91' Mazda Protege. It worked well for a while, but the mounting stud at the bottom was one of those "stainless steel" bolts from Lowe's instead of a real stainless steel bolt. The combination of electrolytic corrosion between the stainless steel mounting bracket and the bolt eroded the threads on the bolt inside the mount until that fateful day about two years ago.

Just as I hit cruise on the parkway the rig suddenly went dead - and after cycling the power I looked up in the mirror just in time to see parts go flying on the bounce. I never found the mast or the whip - but I did find the remnants of the coil and capacitance hat.

I replaced that setup with a tri-magnet mount and the cheap "dummy loads on a stick". On 20 and 17 meters I did not notice any change in either received signals or signal reports. I haven't worked 40 or 80 mobile much because of the trash on 80 and the narrow bandwidth on 40.

The major factor in going to the cheaper antenna system is that it is essentially disposable and I don't wince nearly as much when it hits a low tree limb. It's been in operation almost as long as the expensive antenna was and looking at the smashed coil that is sitting here in the shack with me, I wish I'd started with the cheaper antenna first!

One key to using the magnet mounts is to run a ground strap from the mount to a good ground, inside the trunk in my case. As was pointed out in the original article, safety is a primary concern. Using a good ground strap that is securely attached at both ends reduces the chance of the mag mount becoming a projectile.

An advantage to this system is that I can remove the antenna and put it in the trunk in just a few moments. I use a quick disconnect at the base of the antenna, put the mag mount in the trunk along with the antenna after I undo the whip. I keep 80/40/20 and 17 meter antennas in the trunk so I can change bands about as easily with this system as I could with the big Bugcatcher.

Every mobile operation is different. The vehicles, rigs, operational goals and budget vary from installation to installation. The points to remember cannot be emphasized enough - safety, ease of operation and maintainability. Don't forget to check all the components for damage often!



 
RE: A Little Mobile Information  
by KE1MB on January 5, 2003 Mail this to a friend!
Really good article. But.....
Problim here, I drive a Saturn, in case most of you don't already know, Saturns for the most part are plastic. The only metal is on the roof, trunk and hood. Also to consider is that many hams live in or drive into major citys. Crime is a big concern and anything that can attract attention will. An ant. means that there is something to steal and walk it will. Your radio and damage to your car is not worth that extra S unit because you chose to bolt it down. With a magnet mount you simple pull the thing off your roof, hide it in the trunk or back seat and feel more secure that your car does not stick out. I have been mobile for many years and have found that the multi magnet bases on the roof work well. A Hamstick may not be the best ant. either, but consider that or nothing and a few contacts to New Zealand you can be a happy camper. And oh those lossy glass mount ant. for 2m and 440. Consider that it looks just like everyother old style cell phone ant., that I can drive into that parking garage everyday, and live in a major city where repeaters are a dime a dozen and an HT in the basement can hit one, really does not matter how well it gets out, all that matters is no one notices it. As it must be nice to own lots of land where you can put up anything you want, it must also be nice to be able to drive around with 16ft of rod on your car and only worry about those few things you know not to hit.
 
RE: A Little Mobile Information  
by KE1MB on January 5, 2003 Mail this to a friend!
I did forget to mention safty as with others replys. It is very importaint to understand your radio and all of it's functions. May sound stupid but the voice talker on a 706 can help you keep your eyes on the road and off the radio. Living in a major city also makes driving dangerous due to the high volume of traffic and most importaintly, people who think they can just walk out into traffic with their child and not get hit. One wrong glance to adjust your radio and you could have just hit someone. In these cases playing radio proves more stress that fun and comes a time when shutting it off could mean someones life.

73's
Joe

 
RE: A Little Mobile Information  
by KB9YNB on January 5, 2003 Mail this to a friend!
woo hoo! another chance to be a know-it-all.

mass x velocity(squared) is neither kinetic nor potential energy. HOWEVER, one-half of said quantity is kinetic energy.

I know, I know, "shut up mr. know-it-all and stick your nose back in the book!" I've heard it all before. :^)

Great article on mobile practices. Keep the articles coming!

73,
KB9YNB
 
RE: A Little Mobile Information  
by KG4RUL on January 5, 2003 Mail this to a friend!
R.E. not fusing the 'ground' power leg: My new FT100D came with a wiring harness that has fuses for both legs. Comments?

Dennis - KG4RUL
 
RE: A Little Mobile Information  
by KZ9G on January 5, 2003 Mail this to a friend!

Great article!

Some very good points were mentioned.

But, the only point I'll dispute are the use of the helical antennas you've mentioned (at least at frequencies above 14 MHz). These so-called "dummy loads on a stick" seem to work extremely well above 14 MHz on my vehicles. In fact, the hamsticks I have for 14, 18, 21, and 28 MHz have provided KILLER signals while mounted completely ABOVE my old pickup truck, or just down from the top of my current SUV. Outstanding reports were obtained when they were mounted to a 3/8" x 24 mirror-mount situated on the aluminum boat rack of my truck's cab-level camper shell. This configuration put the whole antenna above the truck. Similar reports (but not quite as good) were had using the same hamsticks mounted to a Hustler stainless ball mount located just below the passenger-side, cargo area window of my Olds Bravada. This configuration put about two-thirds of the antennas above the vehicle. My results have concluded me to believe they're fairly efficient above 14 MHz. Obviously, the mounting location had a lot to do this their performance.

Adequate DC Power is Most Important!

I “remoted” vehicle power to a Bussman fuse buss panel (located in the cab) using a 50A DC circuit and 8 AWG wire taken directly from both battery terminals. The 8 AWG positive lead in my Bravada is routed through a waterproof, 50 amp, DC breaker by Bussman, model number CB185. The breaker is mounted to the wheel well just next to the battery. From the Bussman fuse panel in the cab, I can create several individually fused circuits for radios and the like. Oh, the fuse panel's negative or return buss is bonded to the nearest chassis point, too. I believe it's important to stress grounding and bonding in vehicles. In fact, I occasionally check the integrity of the bonding between the battery's negative terminal and the engine block. Corrosion here can cause an unnecessary system-wide voltage drop throughout the vehicle.

A summary:

1. Mount your mobile antennas as high as possible. If possible, have it completely clear the vehicle.
2. As suggested in this great article, utilize a well-designed DC power circuit with HEAVY gauge wire for any high current need (above 10 amps or so). Well-designed means "fused" or "breakered" near the battery! It also means the power source must be the vehicle's battery terminals.
3. Proper grounding and bonding throughout the vehicle. This can get rather elaborate. Articles abound on this subject.
4. Constantly fight corrosion throughout your vehicle's power and antenna systems.

73!
 
RE: A Little Mobile Information  
by KC0LPV on January 6, 2003 Mail this to a friend!
Arrgh! Dang fraction. Long day. Grrr...

Jim
 
RE: A Little Mobile Information  
by KC0LPV on January 6, 2003 Mail this to a friend!
RE the FT100D with fuses in +/-:

I presume they're putting a lot of faith in your coax braid, should that - fuse blow or be removed without the + fuse. There's no logical reason I can fathom for which you would fuse the ground. Is your home station ground fused...? No. Just the hot leads...

Jim
 
RE: A Little Mobile Information  
by KB0NLY on January 6, 2003 Mail this to a friend!
Great article.

The whole discussion about the fused negative leads on mobiles makes me wonder, if it is such an issue than why does every mobile and even some DC powered base radios have them? And it is not manufacturer specific, Yaesu, Kenwood, Icom, Alinco, Motorola, and others all have fuses in the negative leads. There must be a design reason for it.

Also, when wondering about why that fuse is there in the negative lead, i decided to check out my own mobile installation which uses the supplied DC power leads that came with the radios. The radios are firmly attached, bolted rather, to a metal bracket that i fabricated and installed below the dash in my pickup. The bracket as well as the chassis of the radios have been checked to verify continuity to the ground terminal of the battery, and i also verified that there is continuity from the shield of the coax at the mounting point of the through hole NMO mounts to the battery, and all is well, but when the fuse is removed from the negative lead of one of my mobiles (a new Yaesu) the radio no longer powers up. So my guess is that the fuse is there for a reason, and the chassis ground is somehow independent of the power ground inside the radio? Upon replacing the fuse in the negative lead the radio once again powered up. This doesnt appear to be a fluke, i checked and rechecked all ground points, and without that fuse in the negative lead completing the circuit the radio will not power up.

Obviously though the manufacturers designed it with something particular in mind. Look at Motorola, how many years have they been manufacturing mobile radios, and they too have fuses in the negative lead. Sure, the trunk mount mobiles don't always have a fused ground lead, but the other mobiles that they call dash mounts all have them.

73,

Scott, KBØNLY

 
A Little Mobile Information  
by W8UY on January 6, 2003 Mail this to a friend!
The ground on the Negitive side of your radio is to prevent the engine starter from grounding through your rig should the main vehicle ground fail.

73, de W8UY
 
RE: A Little Mobile Information  
by KB0NLY on January 6, 2003 Mail this to a friend!
To W8UY,

Yep, just read some technical documents from Motorola on protecting the ground lead of two way radio installations. They had the same info, but you summed it up.

Motorola recommends using a fused negative lead from the radios to prevent current flowing through the radio to supply the starter or any other powered accessories in case the Ground cable from the battery to the engine block and/or body of the vehicle becomes loose or disconnected.

I can see now why they would do that. If the radio mounting bracket or shield of the coax is grounded to the body of the vehicle as it should be and the ground cable from the battery to the engine/body becomes disconnected the vehicle will use the radio as a ground. NOT good, i could imagine how much damage would result from the starter drawing through the radio. Hence the fuse to insure that this doesn't happen.

Perhaps some of the installations of commercial trunk mounted radios without fused negative leads that i have seen were installed before they made this standard practice?

Anyway, i happen to know the Chief of Police in the town i live, he happens to be a good friend, and i decided out of curiousity to ask him about having a look at the equipment install that was done by a local Motorola Shop in the new city police Squad car. The system in use does indeed have a fuse in both leads, and as a matter of fact it uses really nice fuse blocks mounted on the firewall before the wiring goes the rest of the way back to the trunk and to the other equipment mounted inside and outside the the vehicle. And there is even also fused connections at the battery to protect the wiring from the battery to the main EQUIPMENT fuse block.

I stress equipment fuse block, because they have a totally seperate fuse block for all the communications and lighting in use.

I would think that to remove, or not use, a fuse in the Negative lead of your mobile equipment is just asking for a visit from ol' Murphy.

73,

Scott, KBØNLY

 
RE: A Little Mobile Information  
by K5DVW on January 6, 2003 Mail this to a friend!
Good article, and I have only a nitpick comment. The 30 tons of force isnt exactly correct with a 8 lb (3.6Kg) mobile rig traveling at 60 Mph (25 m/s). The kenetic energy formula, KE=1/2*m*v*v should be done in metric numbers for it to work out. For English measure, you need a different formula.

You'll get KE=1200 joules which is something like 875 ft-lbs of force. Of course this assumes you are traveling at 0 mph, which you are not if you are in the same car as the flying radio.

Even so, I wouldn't want a flying radio to hit me in the head at any speed.

K5DVW
 
RE: A Little Mobile Information: the science threa  
by KB9YNB on January 6, 2003 Mail this to a friend!
welcome back to the know-it-all.

1/2 * m * v * v can be used to determine kinetic energy in both english and and metric units, as long as you use the correct value for mass: "slugs" for english and kilograms for metric. The values for velocity are generally: feet/second for english and meters/second for metric.

Yes, I know that slugs are usually referred to as: "pounds-mass" and then the unit for force(or weight) is called "pounds-force" I don't know why the mechanical engineers insist on this, but they do.
 
RE: A Little Mobile Information  
by N8IK on January 6, 2003 Mail this to a friend!
Is it ok to put ferrite cores around the spark plug wires and related ignition leads? I seem to recall that some modern ignition systems don't like this. Any auto mechanics out there?

73 de Ian
 
RE: A Little Mobile Information  
by K5DVW on January 6, 2003 Mail this to a friend!
KB9YNB: Hell, I couldn't even spell Kinetic right. Posting too early in the morning I guess. You are right, a physics formula is a formula. Just need to input the correct formatted numbers for the equation.

Slugs are like snails... dang that English system!

Still, watch out for flying radios.

K5DVW
 
RE: A Little Mobile Information  
by K0BG on January 6, 2003 Mail this to a friend!
I'm not going to nit pick the energy, potential, kenetic, or foot pounds, and neither are you if it hits you in the head as a result of an accident.

As for the fused ground leads; it is (as one respondent pointed out) in case the vehicle battery ground lead fails. I had this happen once and luckily the fuse blew saving the rig.

I have never used ferrite beads on sparkplug wires before. But I tried it this time and was surprised. This said, I don't think you could get by with this on ALL wired cars. I've owned 5 turbo cars, and because of their really high spark-energy requirements, I'm not sure it would work without problems.

The Taurus SHO I once owned had a lot of injector noise and beads fixed it okay, but also caused the car to miss occasionally at RPMs over 7,000. So, if you do install beads on the engine controls, keep alert of potential (there's that word again) problems.

Alan, KØBG
 
Negative grounds  
by KC0LPV on January 6, 2003 Mail this to a friend!
Interesting point regarding the starter current. I suppose I never considered that, as I do not see the reason to run a ground cable to the battery negative cable. So long as your battery negative cable to engine block ground, battery negative cable to body ground, and engine block to body grounds are all of sufficient size, there is never a reason to run a seperate accessory ground to the battery.

I can now see the reason for the ground side fuse if you are running ground directly from the battery terminal. Also interesting that the manufacturers seem to have isolated the radio chassis from ground.

Incidentally, I had a similar situation arise in my vehicle. My vehicle has two main ground wires--a large gauge wire to the engine block, and a 10 gauge wire to the body. The engine block also has a couple of large gauge braided ground strap to the body/frame. Anyway, the main (large gauge) ground to engine block wire corroded and broke. I didn't notice anything but a slightly slower crank speed. I noticed that for several months until I was doing some maintenance, and noticed my engine ground cable hanging free several inches from the ring terminal. I can only presume that for the better part of six months (including winter), the only ground my system had was a single ten gauge wire to the body. No overcurrent damage to the wire, amazingly enough.

JD
 
A Little Mobile Information  
by K3ZD on January 6, 2003 Mail this to a friend!
Alan:

I know you hate Hamsticks and I know they must be inefficient but I get consistantly good reports, even on 75 meters, with a Hamstick on the roof of the car with a triple-magmount.

Mark
 
A Little Mobile Information  
by KC0LPV on January 6, 2003 Mail this to a friend!
I hate feeling like I'm hijacking the thread, so perhaps if this goes any farther I'll start a new topic... My apologies to the original poster

I just noticed in the TSB issued by Chrysler for my vehicle, it specifically states:

"DO NOT FUSE THE GROUND LEAD. If the ground-side fuse were to open, the entire supply current would be conducted by the coax shield. This could cause the feedline to overheat, with possible resulting damage."
http://www.neons.org/neontsb/lists/96dohc/../../TSB/08/081698.htm

Have equipment manufacturers made this recommendation obsolete?

Jim
 
RE: A Little Mobile Information  
by K0BG on January 6, 2003 Mail this to a friend!
Rev. Randall P Winchester, WD4HVA, brings up a good point I didn't mention perviously. Look up my call on this site for a pix of my antenna. It is large, heavy, and mounted on a GE Heavy-Duty, cast iron, low band ballmount which nowadays are really hard to find. The stud holding this antenna is made from a number 9 grade 3/8x24 bolt I purchased from the local Catapiller dealer. I cut it with an abrasive cutoff wheel and cleaned up the threads with a grinder. I don't remember the tensil strength, but it is several thousand pounds. If you value your expensive mobile antenna, attach it well and don't use stainless steel studs, or one of unknown quality you bought at the local hardware store.

Thanks Rev.

Alan, KØBG
 
RE: A Little Mobile Information  
by K0BG on January 6, 2003 Mail this to a friend!
Jim, kc0lpv, please read that TSP very carefully. It says to attach the ground lead of the radio to the frame near where the battery ground lead is attached. In this case, yes you do not fuse the ground. But, if it is hooked to the battery negative post as I have suggested, you are asking for trouble if it is not fused.


Alan, KØBG
 
RE: A Little Mobile Information  
by WB2WIK on January 6, 2003 Mail this to a friend!
Nice article! Alan, your mobile installation is pictured on the web with your profile, but a few close-up shots of some of your wiring, etc, would have been interesting. The old "picture's worth a thousand words" thing.

I have three brief comments:

"The antenna works GREAT!" is a statement that should only be made by people having at least two different antennas in or on the same installation. The one that works great is the better one. Making a claim without a reference for comparison is meaningless. All of us have worked New Zealand or wherever while mobile -- it means nothing, since sunspots and propagation are doing 99% of the work. When you make the same contact after the band has closed and nobody else is working anything, then your antenna works great.

Regarding automotive sheet metal being too thin for a heavy-duty ball mount in many cases, I agree. However, if you have the place to install a ball mount, that means you can get at the backside sheet metal, and if so, you can reinforce it. I use my punches to punch 16 ga. CRS (steel) sheet cut to about 6" square first, in the pattern that I'll also use to punch the vehicle fender (or whatever surface I'm mounting the ball on). I place that sheet inside the vehicle, up against the punched fender, and install the ball mount through the vehicle sheet metal AND the added reinforcement sheet behind it. That about doubles the strength of the vehicle wall and keeps it from bending under stress. Cost of this modification: About $1 worth of sheet steel, from the local metal scrap yard. Use electrogalvanized steel if possible, or zinc chromate plated, to slow down oxidation.

Last one: I've "permanently" mounted antennas, or at least antenna mounts, on every car I've owned or leased over the past 25 years. Even on the leased vehicles, when I turned them in, nobody ever said a word about the antenna mount. Just once, when a prospective buyer asked me about the NMO mount in the center of the car roof (I had already unscrewed the antenna), I said the car was "cell phone antenna ready," and he was so happy about that, it helped him make the fast decision to buy the car. I probably could have asked more for it, had I known the antenna mount was going to delight him so much. In all other cases, the subject never came up.

Yes, even on leased vehicles. The dealer is so preoccupied checking your mileage, they don't look at much else unless there's some obvious damage. Turn in the car at night, after dark. Preferably on a lousy night, when it's raining, and it's nearly time for the dealer to close. Then, they look over the whole car in about ten seconds and run inside. Seriously.

I've installed permanent mounts on twelve lease cars and have never paid even a $1 penalty upon turning them in.

WB2WIK/6

 
RE: A Little Mobile Information  
by KE1MB on January 6, 2003 Mail this to a friend!
I cannot resist this but I have to,

Why is shear gain is all that counts? Can there be a chance that there might be other concerns around a setup that have nothing to do with gain. I sure you could list a thousand reasons why a beam and tower are better than an attic dipole, so then why would anyone even use one?

 
A Little Mobile Information  
by KC5CQW on January 6, 2003 Mail this to a friend!
I guess that 20M SSB QRP bicycle moble QSO from the Texas state line to Orlando FL with a Hamstick on my bike rack never happened?!

Well, IT DID!!!! Hamsticks RULE!!!!!
 
RE: A Little Mobile Information  
by W4AN on January 6, 2003 Mail this to a friend!
KC5CQW:

You would have been louder with a Texas Bug Catcher.

73
 
RE: Negative grounds  
by KZ9G on January 7, 2003 Mail this to a friend!
Thanks for mentioning this. Earlier I said, "I believe it's important to stress grounding and bonding in vehicles. In fact, I occasionally check the integrity of the bonding between the battery's negative terminal and the engine block. Corrosion here can cause an unnecessary system-wide voltage drop throughout the vehicle." The "fused" or "breakered" negative leads could possibly prevent damage or meltdown if your radio's DC circuit becomes the primary ground path, instead of the battery to engine block lead. Another reason to inspect the battery to engine block bonding cable!

Let's take this a little further. Besides HF rig power on its own DC circuit, you're running a high power mobile amplifier that draws 100 to 200 amps on its own separate circuit - powered directly from the battery terminals. Wouldn't it make sense to upgrade the battery to engine block bonding cable? Obviously, your alternator is going to be working overtime supplying large amounts of current to keep the battery charged, and for longer periods. Any resistance due to I2R losses and/or corrosion on this bonding lead could cause problems and an unnecessary voltage drop. It just seems to me that large current demands would require deliberate grounding and bonding throughout the vehicle.

Thoughts?

73.
 
RE: Some mobile info  
by W9WHE on January 7, 2003 Mail this to a friend!
K0BG opines:


"There is no excuse you can give me for not drilling holes for a good ball-mount or base plate. Either you're into mobile operation or you're not"

I can think of at least Two VERY GOOD reasons:

1) Plastic body parts; and
2) leased vehicles.


Most of us must adapt the "best way" of doing something to the "best we can do given what we have". For those with plastic, leased or "cherished" vehicles, that means a trunk lip, luggage rack, or magnetic mount.

The philosophy of "my way or its wrong" deters newbies from entering into a new facet of our hobby by telling them, in effect, that "if you can't do it my way, don't do it. Period".

Thus, I humbley offer one more concept to what is already a long list of very good information from K0BG. Don't be afraid to comprimise on things other than safety. After all, at a distance of more than 300 miles, NOBODY can tell the difference between an antenna that is 30% efficent (ball mounted) and one that is 15% efficent (trunk-lip mounted. After all, that's ONLY 3 db, or 1/2 of one "S" unit.

Bottom line for all you potential mobilers, drilling holes in a car body IS NOT REQUIRED for effective and fun mobiling. You WILL WORK THE WORLD with a trunk-lip mounted ham stick or a Yaesu ATAS mounted to your metal luggage rack!
I HAVE!

 
RE: Some mobile info  
by WB2WIK on January 7, 2003 Mail this to a friend!
It's all relative.

Tom Schiller wrote an article two years ago in QST entitled, "Everything Works," detailing how he used an incandescent light bulb to make several solid contacts on HF, and illustrating the point with photographs; then, he went on to show huge stacked beam arrays on 200-foot towers, and attempted to correlate antenna performance to operator satisfaction.

He got a lot of flack for that, all from hams who will never, ever have the big stacked arrays, and all claiming the author couldn't possibly know how much satisfaction they derive from their hobby, regardless of their (undoubtedly poor) antennas.

It's true that nobody can judge another's satisfaction level. I may be dileriously happy, and in complete ecstasy, making a contact with my paper clip antenna system. And I might not even be able to imagine how much more happy I could be (is there something higher than ecstatic?) making better, farther and more contacts using stacked beams on a 200' tower. Especially if I never tried the beams.

It's all relative.

I don't think Alan, or anyone else with any sense, will ever say, "Don't bother operating at all, if you can't do it all the way." I might as well tell my kids to give up all their sports, since they'll never be good enough to turn pro, or make the Olympic teams.

But, until each of us has had the opportunity to push the envelope as far as it can theoretically be pushed, none of us will know what that feels like. I'm happy with my Hustler RM resonators and foldover mast, and 100W mobile HF station. I am quite sure I'd be much happier with the 20' long bug catcher and a mobile kilowatt, just haven't tried that yet. The difference is what you can work when: (1) Others cannot, and (2) After the band has closed and most would just give up.

What you can work when the band's wide open and 5W to a wet string will work long-path doesn't differentiate the players. What you can work after the band's closed and most have disappeared does. And, for many of us, even mobileers, those conditions exist when we're in the car, trying to work somebody!

WB2WIK/6
 
RE: Some mobile info  
by KE1MB on January 7, 2003 Mail this to a friend!
To W9WHE and WB2WIK, thankyou both for making vaild points that many of us contend with.

here's my math

hamstick + magmount = contacts,
contacts = happy
happy = "I'm getting something out of the hobby"


later
joe
 
Don't be intimidated  
by KF6IIU on January 7, 2003 Mail this to a friend!
I've worked about 15 countries and all continents except Africa with an HTX-10, plugged into the lighter, and a Hamstick. I know this won't work for a higher power rig, and the Hamstick wouldn't perform as well on lower bands, but I make the point that you can do a "temporary" installation and still have fun. I don't usually drive and talk at the same time.

Now that 10 is starting to die off with the sunspots I'm starting to think about getting an IC-706 to use the lower bands - this rig will of course have to be connected directly to the battery but I still plan on using hamsticks if I can:

http://home.earthlink.net/~wsanders2/mobileant.htm

I carry a set of small adjstable wrenches to dismount the antenna when the need arises. I am also thinking of ways to use the spare tire mount to support a heavier antenna - it's the only place I'm willing to drill holes in the vehicle.
 
RE: Don't be intimidated  
by WB2WIK on January 7, 2003 Mail this to a friend!
Hamsticks work well on 10m, since they're almost full-sized there; at about 0.2 wavelengths on 10m, they're only a couple of feet short of a full quarter-wave and thus have a high radiation resistance. Even several Ohms of ground resistance doesn't reduce efficiency much when your antenna is 30 or 40 Ohms.

When you get down to 40m, where the Hamstick is only .05 wavelengths long and has very low radiation resistance, you will find the "problem" that Alan K0BG discusses. Several Ohms of ground resistance now becomes a major detriment, as it represents a higher impedance than the antenna itself -- thus meeting the "dummy load on wheels" definition.

BTW, using a $9.95 102" stainless steel CB whip on a ball mount, and a Radio Shack HTX-100 barefoot, in the last solar cycle ('89-90), I worked DXCC in one week from the car, and after a few years of patiently waiting, got 100 countries confirmed from that operation. Best was breaking through a huge pileup to work an OD5 in Lebanon, while I was mobile driving along Pacific Coast Highway in Malibu, CA.

Truly, "anything works" if your timing is good!

WB2WIK/6
 
A Little Mobile Information  
by KD3V on January 7, 2003 Mail this to a friend!
Nice ALAN! GREAT, LOTS of good ideas BUT there is a BIG problem with your assertions. They simply are inaccurate and will mislead people as to what can be done!

e.g.
"Don't use a cheap antenna! Any good, well-built multi-band antenna is going to cost upwards of $250. This is one area you do not want to scrimp on."

WRONG! I use a $40 heavy duty magmount with a $20 whips and I work RELIABLY all over the world! Long path to ZS and VU almost every week for months now. I will give out the callsigns to anyone who asks....

This means that (I quote):
" There is no excuse you can give me for not drilling holes for a good ball-mount or base plate. Either you're into mobile operation or you're not"

is WRONG again!

I am a BIG DX'er (simply means I love it and try to do it all that I can,... and yes.. :) I have been DX and know many DXer's personally) and have been mobiling since 1980. As others have stated, there are plenty of reasons to not drill holes and not doing so says nothing about how "into" mobile operations one is!

Alan, PLEASE give out practical information like much of what you wrote certainly is, but, leave such BASELESS opinions out! They are INVALID and might stop someone from getting on the air.

My results for mobile with hamsticks (an array of them actually) was so good that I duplicated the system on the apartment roof. The $40 Iron Horse triple-5" magmount on a large flattened out computer case over a pair of crossed 3'x10' pieces of chicken-wire for a ground plane. I can take it all down in 10 minutes but I work many stations in ZS on the LONG (14,000 miles) and short path as well as the rest of the world! ONLY 100 watts to do it.

Long path into VU land is about 15,000 miles and I worked a friend there 3 days in a row from the mobile... (I am his favorite mobile! :-) With 5-6 reports on 2 of them. 5-3 on the latter.

NOW for the BIG result... on 40m, with my Hamstick on the roof, I worked a DX contact (split) with V51E and the final report was a 5-5... 3-4 at first but it cleared up as we signed!!

This was months ago! Then last week It was reported to me that he could barely hear me from the mobile but no contact was made... from my car again on 40m... using the hamstick...

My 'array' of hamstick is created with by using the Hustler VP-1 triband adapter. I get one more band than they do because the adapter goes at the base of the magmount and the center whip holds it down and the 3 holes provide the other bands. I use only 2 bands while in motion and 4 while parked! Makes for FAST bandswitching because they can be tuned to interoperate except for 12 & 10 together.

For $80, I get a dualband HF mobile antenna and on my car, a nissan 300ZX, it is mounted totally above the car body in the middle of the roof! Free and clear of any obstructions! Only $120 for 4 bands... no tuning! fast band changes and great results... for lots less than $250.

CHEAP antennas can do a GREAT JOB! Do NOT believe $money$ is the only answer! TRY what you can afford but try to do it right with what you have!

I speak from experience like many of the others who responded.

Alan, we love the information, it is the opinions that can get in the way!

Dave, KD3V
 
RE: A Little Mobile Information  
by K1MKF on January 8, 2003 Mail this to a friend!
Well, IT DID!!!! Hamsticks RULE!!!!!

RE: A Little Mobile Information
by W4AN on January 6, 2003

You would have been louder with a Texas Bug Catcher.

-------------------------------------

Yeah, and if you have 100 watts or a linear or a yagi or from a salt marsh or....

All you need is what it takes at that time on that band from point to point to make a QSO.

Mark
 
RE: Don't be intimidated  
by KB6KGX on January 8, 2003 Mail this to a friend!
Just wanted to share with you... I recently purchased the HTX-10 (not quite the same as your 100, but does what I want it to do).

It was on sale for $89 and I got 25% off THAT as a part-time RS employee!

Anyway... my antenna is a stainless-steel whip and a Larsen NMO-27 coil on the trunk of my Honda Civic. On the weekend of January 14-15, during the 10-meter contest... and darn me that I didn't write down all the callsigns for QSL purposes! OOOHHH!!! But, in the space of two hours on Saturday morning I made contacts in 22 different states and on Sunday got about half-dozen more! Including Canada. I HEARD stations in the UK, Germany, and some South America stations, but they couldn't hear me through the pileups.

Earlier this week I heard a ZL1 station, New Zealand, I believe, but again, he couldn't hear me.

I love 10-meters, for as long as the band holds out, though I'd love to get an FT-900, FT-100D or IC-706MKII, heck... I'd take a Ten-Tec Scout!

Mark
KB6KGX
Huntington Beach, CA
 
RE: A Little Mobile Information  
by W9SWW on January 12, 2003 Mail this to a friend!
the purpose of the fuse in the - line is to prevent accidentaly grounding the starter of the car thru the rig. Seen it and cleaned up after it.
Bill w9sww
 
RE: A Little Mobile Information  
by WB8FPQ on January 12, 2003 Mail this to a friend!
The subject of fusing the negative lead of a mobile installation is actually not too complicated if you just consider the DC situation. The Japanese xcvrs still provide fuses for the negative leads. (I guess they still expect to see some positive ground vehicles...) The US commercial two-way manufacturers do not.

If you follow the explicit instruction to connect the negative lead only to the body sheet metal where the battery negative is attached, you must NOT use a fuse.
Note that NO electrical component in any vehicle from any manufacturer has a fuse in the negative lead.

If you connect the negative lead at the negative battery terminal (not good practice, but sometimes will reduce some on-board noise sources more easily than correcting the OEM's design compromises), it is strongly recommended that you fuse it. Best practice, in this case is to use a fuse one size LARGER than in the positive supply lead.

Discussion on this topic uses up a lot of black (white) board space. See the DaimlerChrysler Technical Service Bulletin (TSB) at your dealer or contact me at the DaimlerChrysler booth at Dayton, or email me at wng@dcx.com for further discussion/help.

Bill Gilmore WB8FPQ
EMC Technical Lead
Dodge Truck Platform Team
DaimlerChrysler Corporation
Detroit, MI

p.s. #43 is not much help at low HF, you can expect some help on the DX bands, but not usually without several turns, #77 or J is much better. (Watch out for saturation on single-ended filters for DC.)
 
Roof Rack mount  
by KD5QLK on January 12, 2003 Mail this to a friend!
KE1MB writes:
" Really good article. But.....
Problim here, I drive a Saturn, in case most of you don't already know, Saturns for the most part are plastic. The only metal is on the roof, trunk and hood."

I solved this problem by getting the saturn roof racks. I bought the removable ones, which go from side to side across the car. They are adaptable, in that they have a channel down the center of the roof racks, so you can put on a bicycle mount, ski racks, etc. I bought screws and bolts that fit in the channel, so I could make my own mounts for the rack. Then I bought some of the metal that is used for framing, and made up a mount to fit in the center of the rear roof rack.
For about a year I just used it as a place to mount my magmount - it was essentially just a flat piece of steel that the magmount stuck to really well - I even put a lip at the back to hold it from sliding backwards. I also put the mount at the BACK of the rack, so that I can still put luggage or whatever between the racks.
Then about a month ago I drilled out the mount and permanently put in an NMO mount. I also took some more metal, and grounded the base electrically TO the roof rack, making the rack itself act as a ground plane. I routed the mini-rg8 through the trim, to the engine compartment, and under the dash.
I now have a very strong NMO mount (stronger than if it went into the thin Saturn roof) and my SWRs are better then they've ever been. I have three vhf/uhf antennas in the back which I swap out depending on what band I need and how big an antenna I want. (If Im going to the mall and know I'll be going into a parking garage, I use the shorty dual band, if I'm long-distance driving I use the MFJ rough-rider,etc.)
I think the roof rack idea should be very viable for a lot of people - It shouldnt be hard to design a chunk of metal to attach to or fit between roof racks, and gives a lot of adaptability for custom mounts. Just remember to plan for other uses of the roof rack, like luggage.
And for what it's worth, I have both leads of heavy guage wire fused at the battery and use anderson powerpoles under the dash.
 
A Little Mobile Information  
by NE2I on January 15, 2003 Mail this to a friend!
A paper from GM on this subject.
http://service.gm.com:8083/techlineinfo/radio.html#top
even has a ic706 and kenwood 742 on it

George NE2I
 
RE: A Little Mobile Information  
by W0LPQ on January 18, 2003 Mail this to a friend!
George, I believe that GM also recommends a fuse in BOTH sides...!!

I did it in my Grand Prix...heard a couple tails of those who did not....and had a radio smoked.

I fused both sides on mine...no hesitation.

Neat article again Alan..

73

Bill, W0LPQ

PS: Steve/WIK....found some info on the other article Alan has...answered my question..!

73

 
RE: A Little Mobile Information  
by K0BG on January 20, 2003 Mail this to a friend!
Dave, KD3V, I repeat myself. If the antenna you are using is only 2% or 3% efficient. and you make contacts, it just goes to show you just how little power it takes, as any QRP operator can tell you.

Being a big DXer, if you are like the rest, you wouldn't even THINK about calling a DX station from you base with out the "BIG" amp on, and the antenna pointed in the correct quadrant.

For what ever reason, the difference between the two types of operation just doesn't compute. I have worked some 300 countries mobile and have busted quite a few big pileups. Sometimes with 100 watts, sometimes with 1,500 watts (yes it was mobile!!), but it isn't the power that is king. Just like a good comedian, it is timing!

As you are no doubt aware, if band conditions are correct, timing becomes less important.

I prefer to be all I can be, but in my case, I use antenna efficiency, not amplifiers.

Alan, KØBG
 
Mobile 20m, power cable  
by WB1W on March 25, 2003 Mail this to a friend!
A great article with many good responses. I'm glad to see so many others interested in mobile operation.

There are many hills where I live, and parking on top of one is like magic. The results are better than any setup I've had at the house. Plus you get to operate with a nice view and no distractions :)

I had some difficulty finding heavy guage cable for the power leads. A friend suggested visiting one of the pro car audio shops (the ones that install loud stereos). They sold me some BIG stuff they called "zero guage". Each lead is about the diameter of a finger - no loss here :)

I use a 20m hamstick mounted on an Iron Horse quad magmount with a quick twist disconnect. It's quick to setup or take down and the magmount is designed to hold at highway speeds (which it has). The rig is grounded to the chassis with 1" ground braid. So far DX has been great.
 
RE: Mobile 20m, power cable  
by N2HBZ on April 13, 2003 Mail this to a friend!
> Wiring is the next most important item. Cigarette
> lighter sockets (auxiliary power outlets) are out!
> No matter the total current draw of your HF rig,
> the minimum wire size should be AWG # 6, and
> connected directly to the battery! This has more
> to do with noise introduction, than it does
> power draw.

I am new to mobile radio...

Can someone elaborate on that last sentence, please. I don't understand why using a lower AWG power cable helps with noise reduction.

 
RE: A Little Mobile Information  
by KD3V on February 14, 2004 Mail this to a friend!
K0BG, you said, "Dave, KD3V, I repeat myself. If the antenna you are using is only 2% or 3% efficient. and you make contacts"

This is not true! a 20m hamstick is much better than 2-3% efficient! You have obviously not heard my signal compared to wire dipoles by my friends in South Africa.

I did one experiment with a 17m hamstick and a full size 1/4 wave on my car (antenna was dead center on the top of the roof).... there was no noticable difference on TX or RX while working a station in Kansas. I swapped them back and forth about 10 times in a 20 minute period and neither he nor I could see an s-meter differences. I could swap them in 20 seconds.

You might be trying to apply values for 80 and 40m hamsticks but they are NOT that bad on 20m! I know because I have tested and compared it to other stations. My reports were always within 1 s-unit of the dipole and often the same.



 
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